1. Field of the Invention
The present invention relates to catheters used within the body. In particular, the present invention relates to a radiopaque marker disposed at the distal end of a catheter for indicating the axial, rotational and yaw position of the distal end when viewed fluoroscopically within the body.
2. Description of the Art
Radiopaque markers are commonly placed on catheters to enhance a physician's ability to view the position of the catheter within bodily vessels or cavities. Circumstances may exist which require a physician to ascertain and improve alignment of the catheter tip after it is advanced in the body. A radiopaque marker provided at a catheter distal end, when viewed fluoroscopically, can enhance a physician's efforts and abilities.
U.S. Pat. No. 4,968,306 to Huss et al. (hereinafter "Huss") shows one conventional manner of marking a catheter distal end. Huss teaches a radiopaque marker band or ring which extends around the catheter near the distal end. The Huss configuration provides a physician the ability to visualize the catheter distal end's general axial location while the catheter is inside a patient's body.
Marking the catheter distal end in the manner as used in Huss does not reveal the precise axial location of the distal tip within a patient's body because the marker is not at the distal tip of the catheter. Moreover, it does not indicate the rotational position of the catheter's distal end.
Both U.S. Pat. No. 4,860,743 and U.S. Pat. No. 5,041,109, both to Abela, show a laser catheter having an end cap made from heat conducting material such as steel. Channels containing optical fibers run through the catheter tip and terminate at a spherical microlens. The channels are symmetrically disposed about the longitudinal axis of the tip. When fluoroscopically viewed the catheter tip will not present a substantially different image profile than a solid tip. Furthermore, the symmetrical shape of the tip does not aid a physician to determine the rotational orientation of the catheter tip.
U.S. Pat. Nos. 5,041,108 and 4,848,336 to Fox et al. (hereinafter "the Fox Patents") show placement of small radiopaque strips of predetermined size positioned on the catheter outer sheath near the distal end. The radiopaque strips aid in determining the rotational and axial position of the catheter tip inside the patient. Both Fox Patents show asymmetrically-placed radiopaque strips on the catheter outer sheath extending in directions parallel with a catheter axis. The Fox Patent configurations require an additional production step of attaching the radiopaque strips to the outer surface of the catheter outer sheath because the strips are not an integral part of the catheter distal tip.
The Fox Patents do not teach how the radiopaque strips are attached to the catheter. It is unclear if the strips are glued to the catheter surface, embedded in the catheter outer sheath, or attached by another technique. If the strips are not attached to the catheter securely, the strips could detach from the catheter while within the body. Such a result could cause a serious complications.
In summation, the above mentioned markers reveal, fluoroscopically, the general axial location of a catheter distal end within a patient's body. The markers of the Fox Patents further reveal the catheter distal tip rotational position. A problem associated with the above radiopaque markers is that none of them reveal the yaw of the catheter distal tip within a patient's body in a manner easily understood when viewed fluoroscopically. Furthermore, it is unclear how the radiopaque markers of the above mentioned apparatus are attached to the catheter.